It sounds like the city may be on shaky ground with that requirement. I don’t know the details of the park obviously, but I would be inclined to challenge the city on legal grounds and bring in wider homes.

Of course, if the lots are just super narrow, and placing any home wider than 12’ would violate the setback requirements between homes that were established when the park was first built, then that’s another story. However, if city is just setting an arbitrary home size of 12’ because that’s what is there right now they’re being ridiculous and I would challenge it.